Abstract We will expand and modernize the Zebrafish International Resource Center (ZIRC) to 1) improve the efficiency of acquisition, maintenance, and distribution of NIH funded resources, 2) promote biosafety, animal welfare, and work safety of animal care staff, and 3) expand the cryopreservation repository and laboratory spaces. ZIRC serves biomedical research as the central repository for wild-type, transgenic, and mutant zebrafish lines, other research materials, and diagnostic health services. ZIRC has outgrown the space of 500 genetic alleles designed for its program 20 years ago due to scientific advancements that vastly increased fish line generation and boosted the number of alleles at ZIRC to 44,937. This growth significantly impacted ZIRC?s quarantine procedures, biosecurity, management of live and cryopreserved lines, and molecular genotyping. Current operations, including animal support, are severely limited by space constraints and a floorplan that restricts workflow and operational support. We propose to improve animal life support, wash room equipment, quarantine, and laboratory areas. 1) We will expand the aquaculture room, modernize the water systems, and add support space. The new systems will be more biosecure, efficient, responsive to changes in water demand, and more accessible for maintenance and repair. 2) To enhance our efficiency and biosecurity, we will build a new wash room with a walk-in washer for parallel processing of equipment. 3) We will add a second quarantine space to enable faster, simultaneous processing of fish imports from facilities with varying biosecurity levels. 4) We will add a new information technology office and expand the cryogenic freezer and laboratory spaces. A new hallway will bypass fish housing for better biosecurity, improved workflow, and connection to the new building additions. 5) We will add a dedicated husbandry research space to expand ZIRC?s research capacity and flexibility. Additional stand-alone fish tank racks and undercounter washers in the fish housing and husbandry research spaces will separate fish with varying health status. In the new research and quarantine spaces, we will install combined flow-through and recirculating water systems to maximize operational flexibility. The proposed improvements will enhance research, personnel safety, operational flexibility, and genotyping capacity. Construction and fixed equipment will modernize the ZIRC?s infrastructure and improve efficiency, thereby limiting costs to researchers and enhancing ZIRC?s services to the biomedical research community.